Abstract: A method for determining sales tax in an automated purchasing system includes the steps of populating data entries in a master transaction record for one or more commodity items. Exemplary populated data entries include material group, cost center code and delivery address. Data corresponding to cost centers are mapped to tax categories representative of abridged functional use classifications. The tax category, material group, and physical location information determined either from the delivery address or from the cost center code are provided from the automated purchasing system to a supplemental software interface. Such data availability is enabled by various combination of user exits, data tables, and importation from temporary memory associated with the automated purchasing system. A tax rate (e.g.